Bathtub drain plug



FIG. 1 illustrates a front view of a bathtub drain plug, according to the inventive design.

FIG. 2 illustrates a plan view of the plug, according to the inventive design; and,

FIG. 3 illustrates a general isometric view of the plug, according to the inventive design. 

The ornamental design for a bathtub drain plug, as shown and described. 